Lenses with variable optical power with optical components which shift perpendicular to the optical axis to vary the optical power have been first described by Louis Alvarez in 1967 (U.S. Pat. No. 3,305,294). Such lenses with variable optical power comprise two optical elements mutually movable in a direction perpendicular to the optical axis and wherein the optical elements have such a form that the combination of the two optical elements results in a lens with different optical powers at different relative positions of the optical elements. The form of the optical elements is described as a cubic element best represented by the basic formula
  z  =            A      2        ⁢          (                                    x            3                    3                +                  xy          2                    )      which formula forms the base of U.S. Pat. No. 3,305,294 and will be set forth below.
This optical principle was later extended to include rotating designs, semi-rotating designs, designs in which only one optical element has to be shifted and designs with additional fifth-order surfaces for correction of spherical aberrations. These variations are described in U.S. Pat. Nos. 3,583,790; 3,305,294; and U.S. Pat. No. 4,650,292 which are incorporated herein by reference in their entirety.
By far the majority of intraocular lenses (hereinafter referred to as “IOLs”) which are implanted in the eye are standard monofocal IOLs or, in lesser numbers, multifocal IOLs with multiple but fixed foci. At present, several promising models of IOLs which can focus the eye driven by natural means (hereinafter referred to as “AIOLs”) are in development in addition to the fixed focus and multifocal IOLs. All these IOLs and AIOLs replace the natural crystalline lens in the human eye to treat, for example, cataracts of the eye or to treat general accommodative and refractive errors of the eye in absence of cataract. AIOLs with shifting cubic optical elements and variations thereon have been described in International Patent Publication Nos. WO 2005/084587 and WO 2006/118452, which are incorporated herein by reference in their entirety.
Such intraocular lenses with shifting optics can produce various undesired variable aberrations depending on, for example, the distribution of optical surfaces, their mutual degree of movement and other aspects of the optical design. For example, a lens of fixed diopter power can be distributed over two shifting optical elements of an accommodating intraocular lens resulting in a variable astigmatism and coma once the elements shift. Such undesired aberrations of the lens itself can be variably corrected according to the inventions set out below in addition to correction of various undesired variable aberrations of the eye itself.
Clearly, it is desirable to have a lens with variable focal length, of which the focusing is driven by natural means, e.g., the ciliary muscle of the eye, to provide the patient with spectacle-free life. However, the human eye does not only defocus at contraction/relaxation of the ciliary muscle but also shows a number of variable aberrations of higher orders which change along with defocus. For purposes of the present disclosure, these aberrations can be defined as “variable accommodation-induced aberrations” and are additional to fixed aberrations of the eye.
Constant and lower-order ocular aberrations of the natural eye can be successfully corrected by ophthalmic lenses, for example, by spectacles or contact lenses with sphero-cylindrical optics, laser treatment of the cornea, etc. Variable accommodation-induced aberrations are well studied and are of significant importance for human vision, but current ophthalmic lenses such as spectacles, contact lenses and IOLs cannot address these variable aberrations. An ideal AIOL, should correct for these variable accommodation-induced aberrations during the focus/defocusing process. In the latter AIOLs the defocus term can be corrected, but an option to correct for other aberrations is likely impossible to be implemented on spherical surfaces moving along the optical axis.
Consequently, the present invention offers the possibility to correct aberrations caused by the natural eye and to correct variable aberrations caused by the intraocular lenses themselves, on their own or in combination such that the combination of fixed diopter powers is distributed over the two optical elements such that the combination of the fixed optical powers is constant regardless of the position of the two optical elements relative to each other.